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Evidence-Based Peer-reviewed Scientific Research Shows that Amblyopia or Lazy Eye Can be Successfully Treated in Older Children and Adults by Susan R. Barry, Ph.D., professor of neurobiology in Biological Sciences at Mount Holyoke College and the author of Fixing My Gaze (June, 2009) and Rachel Cooper of Optometrists Network

New Scientific Research Contradicts Popular Beliefs and Mainstream Medical Practice Theories Regarding Age Limits for the Successful Treatment of Lazy Eye

There is still a general belief that amblyopia can be treated only up to various ages, such as seven (7), ten (10) or twelve (12) years old. This belief persists despite many recent scientific studies and decades of clinical reports on treatments that yield significant visual improvement and best outcomes in older children and even adult amblyopes (see references). Notably, a 2005 multi-site study by the National Eye Institute of the National Institutes of Health demonstrated that children, ages 13 to 17, could improve vision in their amblyopic eye with a combination of glasses, patching, and near vision activities while wearing a patch. No patients over the age of 17 were included in that study so that the report does not set an upper age limit for successful treatment in older children or adults. Since that 2005 study, numerous additional studies have been done on visual improvement of lazy eye in patients over twelve years of age, including adults. Yet, these new discoveries about the treatment of lazy eye at later ages have generally not found their way into general medical eye care practice.

Why then are older amblyopic children, teenagers and adults still being told that nothing can be done for them? There are several reasons, but we will explain three major reasons below.

The outmoded belief that lazy eye must be treated at very young ages or not at all persists to this day due to the following theories and practices:

First, amblyopia develops only during childhood, usually before the age of 8. Since amblyopia develops in childhood, it has been assumed that the disorder can only be treated during early childhood.

Secondly, laboratory studies in the 1960s on animals, such as cats and monkeys, indicated that there was a "critical period" early in life when the visual system develops. In the studies, when one eye of an animal was occluded (covered) shortly after birth, the two-eyed visual system did not develop normally. That is, it was seen that fewer neurons in the visual cortex of the animal's brain responded to the eye that had been occluded after the cover was removed. This lack of response in the animal's brain could be reversed in the study, but only if the occluded eye of the test subject was uncovered or opened during what-was-considered-to-be the brief critical period of development in infancy. These experimental results on animals were then extrapolated to humans and it was then assumed that amblyopia could be reversed only if the human patient was treated very early in life.

However, most children with amblyopia have not been exposed to the severe degree of visual deprivation that was produced in those famous laboratory experiments on cats and monkeys. The experimental animals were deprived of all form vision in one eye often from the first days of life. In contrast, most children with lazy eye receive enough visual stimuli through their affected eye. In these laboratory experiments, the most dramatic negative effects to normal brain and visual development was seen when one eye in the animal was occluded during the first weeks after birth. Animals deprived of sight in one eye at later times showed fewer changes in "brain wiring" or neural pathways. These laboratory studies are a good model for deprivation amblyopia, such as occurs when a congenital cataract is present to block vision in one or both eyes at birth. In these cases, early surgery to remove the cataract is important to restore as much function as possible in the affected eye. However, deprivation amblyopia is present in only one in eighty (1 in 80) amblyopes. The vast majority of amblyopes have strabismic or anisometropic amblyopia. These conditions develop months or even years after birth. Thus, the effects of these conditions on brain wiring may be much less than that observed in the animal experiments. While early intervention is always best, it has been shown in numerous studies, that visual improvement can still occur in older adults.

Last, but not least, the third reason that older amblyopic children and adults are still being told that it is too late for successful treatment of lazy eye is the significant gap in time between when scientific findings are made available and when those findings are put into general practice. In other words, there is a significant time lag between when evidence-based scientific research is released and when it is adopted into professionally recommended treatment guidelines and general health care practice. According to the The Institute of Medicine's (IOM) 2003 report, Priority Areas for National Action: Transforming Health Care Quality, it takes an average of 17 years before new knowledge generated by evidence-based scientific research, such as randomized clinical trials, is incorporated into general health care practice or widespread clinical practiceand even then the application of the knowledge is very uneven.

While the latest scientific research takes time to reach the eye care practitioners, these eye doctors and their staff continue to offer outmoded treatment programs to patients, rather than providing the newly proven treatment programs which give the best outcomes. Eye patching or atropine drops and/or corrective lenses continue to be the most popular cure, but doctor-supervised visual training activities, known as in-office vision therapy are not widely available or frequently recommended. This disturbing time lag and gap in quality of care -- the difference between present proven treatment success rates and those thought to be achievable using best practice guidelines ¯ the difference between present proven treatment success rates and those thought to be achievable using best practice guidelines ¯ have led the Agency for Healthcare Research and Quality (AHRQ) to continue to examine the issues surrounding the adoption of improved clinical practices.

Eye Patching or Atropine Drops Are Often Not Enough

While occlusion (eye patching) or atropine may enhance visual acuity in the amblyopic eye, these techniques do not enhance the patient's ability to use the two eyes together (binocular vision). If the patient does not learn to combine input from the lazy eye and the fellow eye simultaneously, then the beneficial effects of eye patching may be lost. This may explain why twenty-five percent of patients, who are successfully treated with eye patching, experience a decrease in visual acuity in their treated so-called lazy eye during the weeks and months after the patching treatment has ended.

Optometric Vision Therapy Treats Both Eyes and the Entire Visual System

Optometric vision therapy provides additional treatments for all aspects of vision impacted by amblyopia. With vision therapy, for example, the patient engages in visual activities which require the simultaneous use of both the lazy eye and unaffected eye at all distances (near, middle and far range).

Optometric Vision Therapy is Physical Therapy for the Lazy Eye

It has long been accepted that our ability to move and coordinate can be enhanced with training and practice. No one would question the benefits of physical therapy for a patient who has sustained a leg injury. However, for most of the last century, therapy for a lazy eye has been discouraged because it was thought that improvements in vision could not be made past the "critical period." We now know that, thanks to neuroplasticity, we have the ability to change, enhance, and develop many perceptual and visual skills throughout life. Optometric vision therapy is effective in treating people with amblyopia at all ages. No one should be denied treatment simply on the basis of age.

References:

This belief persists despite numerous recent scientific studies and decades of clinical reports on treatments that yield significant visual improvement in older children and even adult amblyopes. Hess RF, Mansouri B, Thompson B. A new binocular approach to the treatment of amblyopia in adults well beyond the critical period of visual development. Restor Neurol Neurosci. 2010;28(6):793-802.

Secondly, laboratory studies in the 1960s on animals, such as cats and monkeys, indicated that there was a "critical period" early in life when the visual system develops.
LeVay S, Wiesel TN, Hubel DH. 1980. The development of ocular dominance columns in normal and visually deprived monkeys. The Journal of Comparative Neurology 191: 1-51.

While early intervention is always best, visual improvement can still occur in older adults. Levi DM. 2005. Perceptual learning in adults with amblyopia: A reevaluation of critical periods in human vision. Developmental Psychobiology 46: 222-232.

Amblyopia affects much more than visual acuity, that is, the ability to read an eye chart. Garzia RP. 1987. Efficacy of vision therapy in amblyopia: A literature review. American Journal of Optometry and Physiological Optics 64: 393-404.